Publications

Abstract

This paper presents a project which tests the hypothesis of the universality of facial expressions of emotions crossculturally and crosslinguistically. First results are presented which contradict the hypothesis.

Abstract

1. Introduction 2. A generative grammar as an algorithm 3. The semantic component 4. Bibliography 1. Introduction Throughout the 20th century up to the present day grammar and semantics have been uneasy bedfellows. A look at the historical background will make it clear how this curious situation came about. 20th-century linguistics has been characterized by an almost exclusive concern with the structure of words, word groups and sentences. This concern was reinforced, especially on the American side of the Atlantic, by the sudden rise and subsequent dominance of behaviorism during the 1920s. It started in psychology but quickly permeated all the human sciences, including linguistics, until the early 1960s, when it collapsed as suddenly as it had arisen.

Abstract

Presupposition is a semantic device built into natural language to make sentences fit for use in certain contexts but not in others. A sentence carrying a presupposition thus evokes a context in which that presupposition is fulfilled. The study of presupposition was triggered by the behavior of natural language negation, which tends to preserve presuppositions either as invited inferences or as entailments. As the role of discourse became more apparent in semantics, presupposition began to be seen increasingly as a discourse-semantic phenomenon with consequences for the logic of language.

Abstract

The property of presuppositions to be sometimes preserved through embeddings, albeit often in a weakened form, is called projection. The projection problem consists in formulating the conditions under which the presuppositions of an embedded clause (a) are kept as presuppositions of the superordinate structure, or (b) remain as an invited inference that can be overruled by context, or (c) are canceled. Over the past 25 years it has been recognized that the projection problem is to be solved in the context of a wider theory of presupposition and discourse incrementation.

Abstract

Logic was discovered by Aristotle when he saw that the semantic behavior of the negation word not is different in sentences with a definite and in those with a quantified subject term. Until the early 20th century, logic remained firmly language-based, but for the past century it has been mainly a tool in the hands of mathematicians, which has meant an alienation from linguistic reality. With the help of new techniques, it is now possible to revert to the logic of language, which is seen as based on a semantic analysis of the logical words (constants) involved. This new perspective, combined with much improved insights into the semantically defined discourse dependency of natural language sentences, leads to a novel and more functionally oriented approach to logic and to a reappraisal of traditional predicate calculus, whose main fault, undue existential import, evaporates when discourse dependency, in particular the presuppositional aspect, is brought into play. Traditional predicate calculus is seen to have a much greater logical power and a much greater functionality than modern predicate calculus. There is also full isomorphism, neglected in modern logic, between traditional predicate calculus and propositional calculus, which raises the question of any possible deeper causes.

Abstract

Virtual objects are objects thought up by a thinking individual. Although 20th-century philosophy has tried to ban them from ontology, they make it impossible to account for the truth of sentences such as Apollo was worshipped in the island of Delos, in which a property is assigned to the nonexisting, virtual entity Apollo. Such facts are the reason why virtual objects are slowly being recognized again.

Abstract

Some predicates are ‘factive’ in that they induce the presupposition that what is said in their subordinate that clause is true.

Abstract

The term ‘donkey sentences’ derives from the medieval philosopher Walter Burleigh, whose example sentences contain mention of donkeys. The modern philosopher Peter Geach rediscovered Burleigh's sentences and the associated problem. The problem is that natural language anaphoric pronouns are sometimes used in a way that cannot be accounted for in terms of modern predicate calculus. The solution lies in establishing a separate category of anaphoric pronouns that refer via the intermediary of a contextually given antecedent, possibly an existentially quantified expression.

Abstract

A discourse domain D is a form of middle-term memory for the storage of the information embodied in the discourse at hand. The information carried by a new utterance u is added to D (u is incremented to D). The processes involved and the specific structure of D are a matter of ongoing research.

Abstract

Discourse semantics (DSx) is based on the fact that the interpretation of uttered sentences is dependent on and co-determined by the information stored in a specialized middle-term cognitive memory called discourse domain (D). DSx studies the structure and dynamics of Ds and the conditions to be fulfilled by D for proper interpretation. It does so in the light of the truth-conditional criteria for semantics, with an emphasis on intensionality phenomena. It requires the assumption of virtual entities and virtual facts. Any model-theoretic interpretation holds between discourse structures and pre-established verification domains.

Abstract

Aristotle's importance in the professional study of language consists first of all in the fact that he demythologized language and made it an object of rational investigation. In the context of his theory of truth as correspondence, he also provided the first semantic analysis of propositions in that he distinguished two main constituents, the predicate, which expresses a property, and the remainder of the proposition, referring to a substance to which the property is assigned. That assignment is either true or false. Later, the ‘remainder’ was called subject term, and the Aristotelian predicate was identified with the verb in the sentence. The Aristotelian predicate, however, is more like what is now called the ‘comment,’ whereas his remainder corresponds to the topic. Aristotle, furthermore, defined nouns and verbs as word classes. In addition, he introduced the term ‘case’ for paradigmatic morphological variation.

Abstract

There is a growing awareness among theoretical linguists and philosophers of language that the linguistic definition of lexical meanings, which must be learned when one learns a language, underdetermines not only full utterance interpretation but also sentence meaning. The missing information must be provided by cognition – that is, either general encyclopedic or specific situational knowledge. This fact crucially shows the basic insufficiency of current standard model-theoretic semantics as a paradigm for the analysis and description of linguistic meaning.

Abstract

The lexical conditions, also known as satisfaction conditions, of a predicate P are the conditions that must be satisfied by the term referents of P for P applied to these term referents to yield a true sentence. In view of presupposition theory it makes sense to distinguish two categories of lexical conditions, the preconditions that must be satisfied for the sentence to be usable in any given discourse, and the update conditions which must be satisfied for the sentence to yield truth.

Abstract

The widely prevailing view that standard bivalent logic is the only possible sound logical system, imposed by metaphysical necessity, has been shattered by the development of multivalent logics during the 20th century. It is now clear that standard bivalent logic is merely the minimal representative of a wide variety of viable logics with any number of truth values. These viable logics can be subdivided into families. In this article, the Kleene family and the PPCn family are subjected to special examination, as they appear to be most relevant for the study of the logical properties of human language.

Abstract

The present paper is part of a large research programme investigating the nature and properties of the predicate logic inherent in natural language. The general hypothesis is that natural speakers start off with a basic-natural logic, based on natural cognitive functions, including the basic-natural way of dealing with plural objects. As culture spreads, functional pressure leads to greater generalization and mathematical correctness, yielding ever more refined systems until the apogee of standard modern predicate logic. Four systems of predicate calculus are considered: Basic-Natural Predicate Calculus (BNPC), Aritsotelian-Abelardian Predicate Calculus (AAPC), Aritsotelian-Boethian Predicate Calculus (ABPC), also known as the classic Square of Opposition, and Standard Modern Predicate Calculus (SMPC). (ABPC is logically faulty owing to its Undue Existential Import (UEI), but that fault is repaired by the addition of a presuppositional component to the logic.) All four systems are checked against seven natural logical intuitions. It appears that BNPC scores best (five out of seven), followed by ABPC (three out of seven). AAPC and SMPC finish ex aequo with two out of seven.

Abstract

The task is designed to elicit vocabulary for simple sounds. The primary goal is to establish how people describe sound and what resources the language provides generally for encoding this domain. More specifically: (1) whether there is dedicated vocabulary for encoding simple sound contrasts and (2) how much consistency there is within a community in descriptions. This develops on materials used in The language of sound

Abstract

The classification of texts and pieces of texts uses the occurrence of, combinations of, words as an important indicator. Not every word or each combination of words gives a clear indication of the classification of a piece of text. Research has been done on methods that select some words or combinations of words that are more indicative of the type of a piece of text. These words or combinations of words are selected from the words and word-groups as they occur in the texts. These more indicative words or combinations of words we call ¿cue-phrases¿. The goal of these methods is to select the most indicative cue-phrases first. The collection of selected words and/or combinations thereof can then be used for training the classification system. To test these selection methods, a number of experiments has been done on a corpus containing cookbook recipes and on a corpus of four-participant meetings. To perform these experiments, a computer program was written. On the recipe corpus we looked at classifying the sentences into different types. Some examples of these types include ¿requirement¿ and ¿instruction¿. On the four-person meeting corpus we tried to learn, using only lexical features, whether a sentence is addressed to an individual or a group. The experiments on the recipe corpus produced good results that showed that, a number of, the used cue-phrase selection methods are suitable for feature selection. The experiments on the four-person meeting corpus where less successful in terms of performance off the classification task. We did see comparable patterns in selection methods, and considering the results of Jovanovic we can conclude that different features are needed for this particular classification task. One of the original goals was to look at ¿addressee¿ in discussions. Are sentences more often addressed to individuals inside discussions compared to outside discussions? However, in order to be able to accomplish this, we must first identify the segments of the text that are discussions. It proved hard to come to a reliable specification of discussions, and our initial definition wasn¿t sufficient.

Abstract

The problem of identifying and correcting confusibles, i.e. context-sensitive spelling errors, in text is typically tackled using specifically trained machine learning classifiers. For each different set of confusibles, a specific classifier is trained and tuned. In this research, we investigate a more generic approach to context-sensitive confusible correction. Instead of using specific classifiers, we use one generic classifier based on a language model. This measures the likelihood of sentences with different possible solutions of a confusible in place. The advantage of this approach is that all confusible sets are handled by a single model. Preliminary results show that the performance of the generic classifier approach is only slightly worse that that of the specific classifier approach

Abstract

In the context of confusible disambiguation (spelling correction that requires context), the synchronous back-off strategy combined with traditional n-gram language models performs well. However, when alternatives consist of a different number of tokens, this classification technique cannot be applied directly, because the computation of the probabilities is skewed. Previous work already showed that probabilities based on different order n-grams should not be compared directly. In this article, we propose new probability metrics in which the size of the n is varied according to the number of tokens of the confusible alternative. This requires access to n-grams of variable length. Results show that the synchronous back-off method is extremely robust. We discuss the use of suffix trees as a technique to store variable length n-gram information efficiently.

Abstract

This paper describes ongoing research aiming at the description of variation in speech as represented by asynchronous articulatory features. We will first illustrate how distances in the articulatory feature space can be used for event detection along speech trajectories in this space. The temporal structure imposed by the cosine distance in articulatory feature space coincides to a large extent with the manual segmentation on phone level. The analysis also indicates that the articulatory feature representation provides better such alignments than the MFCC representation does. Secondly, we will present first results that indicate that articulatory features can be used to probe for acoustic differences in the onsets of Dutch singulars and plurals.

Abstract

This paper builds on previous work that aims at unraveling the structure of the speech signal by means of using probabilistic representations. The context of this work is a multi-pass speech recognition system in which a phone lattice is created and used as a basis for a lexical search in which symbolic mismatches are allowed at certain costs. The focus is on the optimization of the costs of phone insertions, deletions and substitutions that are used in the lexical decoding pass. Two optimization approaches are presented, one related to a multi-pass computational model for human speech recognition, the other based on a decoding in which Bayes’ risks are minimized. In the final section, the advantages of these optimization methods are discussed and compared.

Abstract

The Papuan languages of the central Solomon Islands are a negatively defined areal grouping: They are those four or possibly five languages in the central Solomon Islands that do not belong to the Austronesian family. Bilua (Vella Lavella), Touo (Rendova), Lavukaleve (Russell Islands), Savosavo (Savo Island) and possibly Kazukuru (New Georgia) have been identified as non-Austronesian since the early 20th century. However, their affiliations both to each other and to other languages still remain a mystery. Heterogeneous and until recently largely undescribed, they present an interesting departure from what is known both of Austronesian languages in the region and of the Papuan languages of the mainland of New Guinea.

Abstract

The present study shows that [t] consonants are affected by probabilistic factors in a syllable-timed language as French, and in spontaneous as well as in journalistic speech. Study 1 showed a word bigram frequency effect in spontaneous French, but its exact nature depended on the corpus on which the probabilistic measures were based. Study 2 investigated journalistic speech and showed an effect of the joint frequency of the test word and its following word. We discuss the possibility that these probabilistic effects are due to the speaker’s planning of upcoming words, and to the speaker’s adaptation to the listener’s needs.

Abstract

A dominant hypothesis in empirical research on the evolution of language is the following: the fundamental difference between animal and human communication systems is captured by the distinction between regular and more complex non-regular grammars. Studies reporting successful artificial grammar learning of nested recursive structures and imaging studies of the same have methodological shortcomings since they typically allow explicit problem solving strategies and this has been shown to account for the learning effect in subsequent behavioral studies. The present study overcomes these shortcomings by using subtle violations of agreement structure in a preference classification task. In contrast to the studies conducted so far, we use an implicit learning paradigm, allowing the time needed for both abstraction processes and consolidation to take place. Our results demonstrate robust implicit learning of recursively embedded structures (context-free grammar) and recursive structures with cross-dependencies (context-sensitive grammar) in an artificial grammar learning task spanning 9 days. Keywords: Implicit artificial grammar learning; centre embedded; cross-dependency; implicit learning; context-sensitive grammar; context-free grammar; regular grammar; non-regular grammar

Abstract

This paper describes a new flexible delexicalization method based on glottal excited parametric speech synthesis scheme. The system utilizes inverse filtered glottal flow and all-pole modelling of the vocal tract. The method provides a possibility to retain and manipulate all relevant prosodic features of any kind of speech. Most importantly, the features include voice quality, which has not been properly modeled in earlier delexicalization methods. The functionality of the new method was tested in a prosodic tagging experiment aimed at providing word prominence data for a text-to-speech synthesis system. The experiment confirmed the usefulness of the method and further corroborated earlier evidence that linguistic factors influence the perception of prosodic prominence.

Abstract

In this chapter, I review my EEG research on comprehending sentences in context from a pragmatics-oriented perspective. The review is organized around four questions: (1) When and how do extra-sentential factors such as the prior text, identity of the speaker, or value system of the comprehender affect the incremental sentence interpretation processes indexed by the so-called N400 component of the ERP? (2) When and how do people identify the referents for expressions such as “he” or “the review”, and how do referential processes interact with sense and syntax? (3) How directly pragmatic are the interpretation-relevant ERP effects reported here? (4) Do readers and listeners anticipate upcoming information? One important claim developed in the chapter is that the well-known N400 component, although often associated with ‘semantic integration’, only indirectly reflects the sense-making involved in structure-sensitive dynamic composition of the type studied in semantics and pragmatics. According to the multiple-cause intensified retrieval (MIR) account -- essentially an extension of the memory retrieval account proposed by Kutas and colleagues -- the amplitude of the word-elicited N400 reflects the computational resources used in retrieving the relatively invariant coded meaning stored in semantic long-term memory for, and made available by, the word at hand. Such retrieval becomes more resource-intensive when the coded meanings cued by this word do not match with expectations raised by the relevant interpretive context, but also when certain other relevance signals, such as strong affective connotation or a marked delivery, indicate the need for deeper processing. The most important consequence of this account is that pragmatic modulations of the N400 come about not because the N400 at hand directly reflects a rich compositional-semantic and/or Gricean analysis to make sense of the word’s coded meaning in this particular context, but simply because the semantic and pragmatic implications of the preceding words have already been computed, and now define a less or more helpful interpretive background within which to retrieve coded meaning for the critical word.

Abstract

A not uncommon assumption in psycholinguistics is that the N400 directly indexes high-level semantic integration, the compositional, word-driven construction of sentence- and discourse-level meaning in some language-relevant unification space. The various discourse- and speaker-dependent modulations of the N400 uncovered by us and others are often taken to support this 'compositional integration' position. In my talk, I will argue that these N400 modulations are probably better interpreted as only indirectly reflecting compositional sense-making. The account that I will advance for these N400 effects is a variant of the classic Kutas and Federmeier (2002, TICS) memory retrieval account in which context effects on the word-elicited N400 are taken to reflect contextual priming of LTM access. It differs from the latter in making more explicit that the contextual cues that prime access to a word's meaning in LTM can range from very simple (e.g., a single concept) to very complex ones (e.g., a structured representation of the current discourse). Furthermore, it incorporates the possibility, suggested by recent N400 findings, that semantic retrieval can also be intensified in response to certain ‘relevance signals’, such as strong value-relevance, or a marked delivery (linguistic focus, uncommon choice of words, etc). In all, the perspective I'll draw is that in the context of discourse-level language processing, N400 effects reflect an 'overlay of technologies', with the construction of discourse-level representations riding on top of more ancient sense-making technology.

Abstract

This book provides an overview of the grammatical structure of the language Yurakaré, an unclassified and previously undescribed language of central Bolivia. It consists of 8 chapters, each describing different aspects of the language. Chapter 1 is an introduction to the Yurakaré people and their language. Chapter 2 describes the phonology of the language, from the individual sounds to the stress system. In chapter 3 the morphology of Yurakaré is introduced, i.e. the parts of speech, and the different morphological processes. Chapter 4 is a description of the noun phrase and contains information about nouns, adjectives, postpositions and quantifiers. It also discusses the categories associated with the noun phrase in Yurakaré, such as number, possession, collectivity/distributivity, diminutive. In chapter 5, called 'Verbal agreement, voice and valency' there is a description of the argument structure of predicates, how arguments are expressed and how argument structure can be altered by means of voice and valency-changing operations such as applicatives, causative and middle voice. In chapter 6 there is an overview of verbal morphology, apart from the morphology associated with voice, valency and cross-reference discussed in chapter 5. There is also a description of adverbs in the language in this chapter. Chapter 7 discusses formal and functional properties of modal and aspectual enclitics. In chapter 8, finally, the structure of the clause (both simplex and complex) is discussed, including the switch-reference system and word order. The book ends with two text samples.

Abstract

Pitch, intonation, and speech rate were analyzed in a collection of everyday speech heard by one Dutch infant between the ages of six and nine months. Components of each of these variables were measured in the speech of three adult speakers (mother, father, baby-sitter) when they addressed the infant, and when they addressed another adult. The results are in line with previously reported findings which are usually based on laboratory or prearranged settings: infant-directed speech in a natural setting exhibits more pitch variation, a larger number of simple intonation contours, and slower speech rate than does adult-directed speech.

Abstract

The linguistic category of irrealis does not show stable semantics across languages. This makes it difficult to formulate general statements about this category, and it has led some researchers to reject irrealis as a cross-linguistically valid category. In this paper we look at the semantics of the irrealis category of Yurakaré, an unclassified language spoken in central Bolivia, and compare it to irrealis semantics of a number of other languages. Languages differ with respect to the subcategories they subsume under the heading of irrealis. The variable subcategories are future tense, imperatives, negatives, and habitual aspect. We argue that the cross-linguistic variation is not random, and can be stated in terms of an implicational scale.

Abstract

Dutch distinguishes at least four sentence types: statements and questions, the latter type being subdivided into wh-questions (beginning with a question word), yes/no-questions (with inversion of subject and finite), and declarative questions (lexico-syntactically identical to statement). Acoustically, each of these (sub)types was found to have clearly distinct global F0-patterns, as well as a characteristic distribution of final rises [1,2]. The present paper explores the separate contribution of parameters of global downtrend and size of accent-lending pitch movements versus aspects of the terminal rise to the human identification of the four sentence (sub)types, at various positions in the time-course of the utterance. The results show that interrogativity in Dutch can be identified at an early point in the utterance. However, wh-questions are not distinct from statements.

Abstract

Listeners require context to understand the casual pronunciation variants of words that are typical of spontaneous speech (Ernestus et al., 2002). The present study reports two auditory lexical decision experiments, investigating listeners' use of semantic contextual information in the comprehension of unreduced and reduced words. We found a strong semantic priming effect for low frequency unreduced words, whereas there was no such effect for reduced words. Word frequency was facilitatory for all words. These results show that semantic context is relevant especially for the comprehension of unreduced words, which is unexpected given the listener driven explanation of reduction in spontaneous speech.

Abstract

The seemingly effortless switching between languages and the merging of two languages into a coherent utterance is a hallmark of bilingual language processing, and reveals the flexibility of human speech and skilled cognitive control. That skill appears to be available not only to speakers when they produce language-switched utterances, but also to listeners and readers when presented with mixed language information. In this chapter, we review electrophysiological studies in which Event-Related Potentials (ERPs) are derived from recordings of brain activity to examine the neurocognitive aspects of comprehending and producing mixed language. Topics we discuss include the time course of brain activity associated with language switching between single stimuli and language switching of words embedded in a meaningful sentence context. The majority of ERP studies report that switching between languages incurs neurocognitive costs, but –more interestingly- ERP patterns differ as a function of L2 proficiency and the amount of daily experience with language switching, the direction of switching (switching into L2 is typically associated with higher switching costs than switching into L1), the type of language switching task, and the predictability of the language switch. Finally, we outline some future directions for this relatively new approach to the study of language switching.

Abstract

Recent studies using phoneme detection tasks have shown that spoken-language processing is neither facilitated nor interfered with by optional assimilation, but is inhibited by violation of obligatory assimilation. Interpretation of these results depends on an assessment of their generality, specifically, whether they also obtain when listeners are processing nonnative language. Two separate experiments are presented in which native listeners of German and native listeners of Dutch had to detect a target fricative in legal monosyllabic Dutch nonwords. All of the nonwords were correct realisations in standard Dutch. For German listeners, however, half of the nonwords contained phoneme strings which violate the German fricative assimilation rule. Whereas the Dutch listeners showed no significant effects, German listeners detected the target fricative faster when the German fricative assimilation was violated than when no violation occurred. The results might suggest that violation of assimilation rules does not have to make processing more difficult per se.

Abstract

Lexical recognition is typically slower in L2 than in L1. Part of the difficulty comes from a not precise enough processing of L2 phonemes. Consequently, L2 listeners fail to eliminate candidate words that L1 listeners can exclude from competing for recognition. For instance, the inability to distinguish /r/ from /l/ in rocket and locker makes for Japanese listeners both words possible candidates when hearing their onset (e.g., Cutler, Weber, and Otake, 2006). The L2 disadvantage can, however, be dispelled: For L2 listeners, but not L1 listeners, L2 speech from a non-native talker with the same language background is known to be as intelligible as L2 speech from a native talker (e.g., Bent and Bradlow, 2003). A reason for this may be that L2 listeners have ample experience with segmental deviations that are characteristic for their own accent. On this account, only phonemic deviations that are typical for the listeners’ own accent will cause spurious lexical activation in L2 listening (e.g., English magic pronounced as megic for Dutch listeners). In this talk, I will present evidence from cross-modal priming studies with a variety of L2 listener groups, showing how the processing of phonemic deviations is accent-specific but withstands fine phonetic differences.

Abstract

Utilization of computer tools in linguistic research has gained importance with the maturation of media frameworks for the handling of digital audio and video. The increased use of these tools in gesture, sign language and multimodal interaction studies has led to stronger requirements on the flexibility, the efficiency and in particular the time accuracy of annotation tools. This paper describes the efforts made to make ELAN a tool that meets these requirements, with special attention to the developments in the area of time accuracy. In subsequent sections an overview will be given of other enhancements in the latest versions of ELAN, that make it a useful tool in multimodality research.

Abstract

A number of serious reasons will convince an increasing amount of researchers to store their relevant material in centers which we will call "language resource archives". They combine the duty of taking care of long-term preservation as well as the task to give access to their material to different user groups. Access here is meant in the sense that an active interaction with the data will be made possible to support the integration of new data, new versions or commentaries of all sort. Modern Language Resource Archives will have to adhere to a number of basic principles to fulfill all requirements and they will have to be involved in federations to create joint language resource domains making it even more simple for the researchers to access the data. This paper makes an attempt to formulate the essential pillars language resource archives have to adhere to.

Abstract

Set is widely used as a kind of basic data structure. However, when it is used for large scale data set the cost of storage, search and transport is overhead. The bloom filter uses a fixed size bit string to represent elements in a static set, which can reduce storage space and search cost that is a fixed constant. The time-space efficiency is achieved at the cost of a small probability of false positive in membership query. However, for many applications the space savings and locating time constantly outweigh this drawback. Dynamic bloom filter (DBF) can support concisely representation and approximate membership queries of dynamic set instead of static set. It has been proved that DBF not only possess the advantage of standard bloom filter, but also has better features when dealing with dynamic set. This paper proposes a time-dependent multiple bit-strings bloom filter (TMBF) which roots in the DBF and targets on dynamic incremental set. TMBF uses multiple bit-strings in time order to present a dynamic increasing set and uses backward searching to test whether an element is in a set. Based on the system logs from a real P2P file sharing system, the evaluation shows a 20% reduction in searching cost compared to DBF.

Abstract

Although sign language-using communities exist in all areas of the world, few sign languages have been documented in detail. Sign languages occur in a variety of sociocultural contexts, ranging from sign languages used in closed village communities to officially recognized national sign languages. They may be grouped into language families on historical grounds or may participate in various language contact situations. Systematic cross-linguistic comparison reveals both significant structural similarities and important typological differences between sign languages. Focusing on information from non-Western countries, this article provides an overview of the sign languages of the world.